A senior church leader has called on politicians to stop using "alarmist and evocative" language in the debate on immigration amid controversy about a UKIP poster campaign.

UKIP leader Nigel Farage launched his party's European election bid in Sheffield amid criticism over the posters, which were labelled "racist" by Labour MP Mike Gapes.

The leader of the Catholic Church in England and Wales, Cardinal Vincent Nichols, did not refer to any political party but said it was wrong to use expressions that suggest "dismay or distress at all these people coming to this country".

"What I would appeal today is that the debate about immigration is done with a sense of realism and a sense of respect - and that it is not cushioned in expressions which are alarmist and evocative of anger or of dismay or distress at all these people coming to this country," he said.

"We have to grow to appreciate the richness that immigration brings.

"The reality is that the vast majority of migrants to this country add to our wellbeing."

One of the posters which cost UKIP £1.5m

In the run-up to the May 22 poll, hundreds of UKIP posters on billboards across the country will carry the words: "British workers are hit hard by unlimited foreign labour".

Mr Farage was unapologetic following the criticism, saying: "These posters are a hard-hitting reflection of reality as it is experienced by millions of British people struggling to earn a living outside the Westminster bubble."

Countering claims in one of the posters, Poland's ambassador in London says the UK is not as attractive as it once was for Polish workers.

"This huge wave of people who came to EU countries trying to get well-paid jobs is over now," Witold Sobkow told The Independent.

"There are more opportunities in Poland, we have had huge economic success, wages are higher in Poland now and there are more jobs in many parts of Poland, so I think this is over."

Video:UKIP Boost Ahead Of Euro Elections

Meanwhile, Liberal Democrat leader Nick Clegg said he accepted the pro-European case lacked "volume" - and he called for Labour and Conservative MPs to unite to counter UKIP's message.

"If Labour is still a pro-European party, it needs to come off the fence. Tory modernisers must risk the wrath of their backbenchers and speak out," he said.